This invention relates to a solar heat collector wherein the heat absorbing surface primarily consists of a multiplicity of fins in intimate, heat transfer contact with a conduit used to supply a fluid medium to undergo heating by solar radiation. More particularly, the present invention relates to such a solar heat collector wherein the fins include bent portions to receive beam radiation from the sun, to increase the flux of heat to the fluid circulating in the conduit and electrical heating means within the collector to maintain the temperature therein above the freezing point of the fluid.
The principle of solar energy collectors is well known in the art which includes a description and analysis in the publication "Solar Energy Thermal Processes" by Duffie and Beckman, published by John Wiley & Sons in 1974. Solar collectors basically consist of an enclosure containing a metal plate in contact with fluid passageways. These passageways are integral with the plate or provided by tubes joined in some manner so as to be in a heat-conductive relation with the plate. One or more transparent covers permits solar radiation to reach the plate and prevent conductive heat transfer away from the enclosure. One particular known cover plate consists of two glass plates separated by a space that has been evacuated and maintained airtight. The enclosure is arranged so that the glass plate cover faces the sun while the opposite side is insulated to prevent convection losses. The remaining sides of the enclosure are insulated and sealed to prevent atmospheric contamination and the infiltration of moisture.
The use of a collector surface in the form of a single flat plate has certain distinct disadvantages. The effective heat absorbed by the plate and conduction of heat to the fluid within the tubes are dependent upon efficient flux of heat, the thickness of the plate and the distance between two adjoining tubes carrying the fluid. In view of these parameters, it was possible to build an efficient flat plate collector so long as the plate was made of a highly conductive material, such as copper, of substantial thickness and with closely-spaced tubes joined to the copper plate. However, because of the design and material requirements, it is not possible to produce a collector of this type economically.